A windshield washer reservoir typically comprises a hollow reservoir, an inlet through which windshield washer fluid is added to fill the reservoir and an exit from which the fluid is delivered through a pump to a windshield washer nozzle.
In a motor vehicle, the space allocated to a windshield reservoir is frequently limited. The shape of a reservoir to fit inside a vehicle may be elongated with the length of the reservoir being greater than its height. A vent may be added to the reservoir distant from the filling inlet to facilitate the liquid filling process. When a liquid is introduced into the reservoir, air inside the reservoir is displaced. Removal of air through the inlet may be inadequate limiting the rate of filling of liquid. Another problem is that air may become trapped within the reservoir. A vent allows the air to be removed from the reservoir (e.g. displaced) so as to accommodate the incoming liquid.
A problem that arises with the addition of a vent to a reservoir is that it introduces a means for liquid to exit the reservoir. Upon acceleration or deceleration of a vehicle liquid may splash outside the reservoir. Such leakage leads to the reduction of windshield washing capability and is aesthetically unpleasing. Thus, in some applications, it may be advantageous to provide a restriction to limit the quantity of liquid that may exit the vent outlet.